achromatic stimulus
stimulus that, under the prevailing conditions of adaptation, gives rise to an achromatic colour
Note 1 to entry: In the colorimetry of object colours, the colour stimulus produced by the perfect reflecting diffuser or perfect transmitting diffuser is usually considered to be an achromatic stimulus for all sources, except for those that appear to be highly chromatic.
Note 2 to entry: This entry was numbered 845-03-06 in IEC 60050-845:1987.
Note 3 to entry: This entry was numbered 17-12 in CIE S 017:2011.